Diseases such as lymphedema and venous insufficiency can often result in the pooling of bodily fluids in areas of the body distal from the heart. Venous insufficiency can result when the superficial veins of an extremity empty into the deep veins of the lower leg. Normally, the contractions of the calf muscles act as a pump, moving blood into the popliteal vein, the outflow vessel. Failure of this pumping action can occur as a result of muscle weakness, overall chamber size reduction, valvular incompetence and/or outflow obstruction. Each of these conditions can lead to venous stasis and hypertension in the affected area.
Fluid accumulation can be painful and debilitating if not treated. Fluid accumulation reduce oxygen transport, interfere with wound healing, provide a medium that supports infections or even result in the loss of a limb if left untreated.
Compression devices are often used in the treatment of venous insufficiency by moving the accumulated bodily fluids. Compression devices that improve pressure accuracy by using a pressure lookup table to account for a pressure drop in one or more valves are known in the art and are described in, for example, U.S. patent application Ser. No. 11/745,700.
A pressure lookup table compensates for a pressure difference at a transducer and a device cell. As pressure drop is a function of the desired pressure, a lookup table may be utilized to determine the pressure offset for a given setting. This method effectively improves pressure accuracy when inflating a single cell, however there is a significant effect on a particular cell's pressure when subsequent cells are inflated. This typically results in an undesirable overpressure condition where a cell's pressure rises substantially above the desired value.